The present invention relates to rotary positive displacement machines, particularly, but not solely, for use in heat pumps.
In conventional small heat pumps no energy is recovered from vapour passing from the condenser to the evaporator.
It would be desirable to be able to recover energy from fluid between the condenser and the evaporator in a heat pump cycle.
It would also be desirable to provide a machine which allows vapour from the condenser to do work as it expands.
It would also be desirable to provide a machine for performing both compression and expansion.
The invention is based on a rotary positive displacement machine comprising:
a stator having a circular cylindrical internal surface delimiting an operating chamber, the stator having fluid inlet/outlet ports;
a rotor in the operating chamber, the rotor being mounted so as to be rotatable relative to the stator about the axis of the said internal surface, the rotor having a cylindrical external surface, the said axis passing through the rotor, a generatrix of the external surface being adjacent to the said internal surface, and a diametrically opposite generatrix being spaced from the said internal surface;
a sealing member projecting substantially radially through a slot in the stator into the operating chamber and being movable substantially radially, the sealing member extending parallel to the said axis and having a length substantially equal to that of the rotor; and
means for keeping the radially inner end of the sealing member adjacent the external surface of the rotor.
In one aspect the invention provides a rotary positive displacement machine a set forth in claim 1.
In another aspect the invention provides a rotary positive displacement machine as set forth in claim 11.